Abstract

Lymphatic filariasis is a global problem, with about 120 million people infected worldwide in 80 endemic countries. Filarial infections have been associated with the development of strongly polarized Type 2 host immune response and a severe impairment of type 1 cytokine production in humans. The aim of this study was to assess the immune responsiveness of patients with lymphatic filariasis, by studying their cytokine secretion profile. Samples were collected from 45 patients of different clinical manifestations such as chronic with lymphatic pathology (n=15), microfilaraemics (n=15) and endemic controls (n=15). Fifteen samples from non-endemic healthy controls were also included in the study. The levels of interleukin-2 (IL-2) and interferon-γ (IFNγ) for type 1 and interleukin-4, interleukin-5 and interleukin-10 (IL-4, IL-5 and IL-10) for type 2 responses were estimated by ELISA in peripheral blood mononuclear cell (PBMC) culture supernatants. The cells were cultured and sensitised with purified W. bancrofti extracted micro filarial antigens. The results showed the induction of type 2 immune responses with down regulation of type 1 responses. Levels of IL-4, IL-5 and IL-10 were increased in all chronic, microfilaraemic and endemic control cases. The analysis of data showed significant decrease in IL-2 (p<0.01) and IFNγ (p<0.02) levels in microfilaraemic patients as compared to chronic and endemic control cases. Our findings suggested an attenuated T-helper 1 response in patients with filariasis. The data presented here suggest a complex relationship between the host immune response and parasite establishment and survival that cannot be simply ascribed to the Th1/Th2 paradigm. There is an up regulation of IL-4, IL-5 and IL-10 expression in patients with lymphatic filariasis and a simultaneous decrease in levels of the interferon-gamma and IL-2. The profile of different cytokines in this study may prove useful in further stage-specific diagnosis of filarial patients of different clinical manifestations.